Method of producing metallic member

ABSTRACT

A method of producing a metallic member that reduces the burden on a mold during molding is provided. The method of producing the metallic member according to the present invention includes the step of forming a cup-like member by applying a load to a metallic plate member, and the step of forming a plurality of protrusions at an opening end portion of the cup-like member by placing the cup-like member into a mold.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of producing a metallicmember. More particularly, the present invention relates to a method ofproducing a metallic member having a plurality of protrusions of, forexample, a gear member or a vibration member of a vibration wave drivingapparatus.

2. Description of the Related Art

As a metallic member in which a plurality of protrusions are arranged, avibration member for a vibration wave driving apparatus discussed inJapanese Patent Laid-Open No. 07-135785 is available. The vibrationmember is an annular or a disc-shaped member. Many protrusions like theteeth of a comb are provided at one surface (upper surface) of thevibration member, and a base not having teeth of a comb are provided atthe opposite surface (lower surface) of the vibration member. Aring-like piezoelectric element is joined to the lower surface of thebase. In this type of vibration member, the many protrusions are formedby a forging method or a method of cutting many radial grooves using agrinding tool or a milling cutter having the shape of a disc (a grindingmethod or a cutting method). The role of the protrusions is to increasevibration displacement when rotating a moving member by transmittingvibration of the vibration member to the moving member by frictionforce. Depending upon use, a hole extending through an output shaft isprovided in the center of the vibration member.

As another example of a metallic member having a plurality ofprotrusions, a gear such as that discussed in Japanese Patent Laid-OpenNo. 2001-205385 is available. The gear (such as a bevel gear) havingteeth as the plurality of protrusions has a hole portion that does hothave a core for passing a shaft therethrough. The teeth of the gear mayalso be formed by the cutting method or the grinding method, or by theforging method using a pressing device.

SUMMARY OF THE INVENTION

The forging method is lower in cost than the cutting method and thegrinding method because the forging method is a processing method thatcan be simplified.

For forming many protrusions by the forging method, it is possible toprovide an annular or a disc-shaped processing object in which a pipe ora round bar is cut into round slices, and to form the protrusions on theprocessing object by directly subjecting the processing object to apressing operation. FIGS. 6A and 6B schematically illustrate states inwhich protrusions are formed on a processing object 111 by the forgingmethod. FIG. 6A is a sectional view, and FIG. 6B is a perspective view.As shown in FIG. 6A, the circular processing object 111 is used, and isinserted into an inside diameter portion of a die ring 123 (serving asan outer frame of a stationary mold (female mold)) to directly form theprotrusions.

However, this method has the following problems. When a punch 122(serving as a pressing mold (male mold)) contacts the processing object111, stress applied to the female mold is instantaneously increased. Asa result, the female mold tends to break. In addition, a force forreducing the thickness of the processing object 111 interposed betweenthe punch 122 and the female mold is applied to the molds at the sametime that pressure is applied. Therefore, a large total load is requiredfor a molding operation. From this viewpoint also, the molds tend tobreak. In particular, the stress concentrates at a thin-walled portion124 a of a die 124 having recesses and protrusions. The thin-walledportion 124 a is provided for forming grooves (between the protrusions)in an outer-peripheral lower surface of the disc-shaped processingobject. The smaller the widths of the grooves, the thinner thethin-walled portion 124 a, thereby reducing the strength of thethin-walled portion 124 a. Therefore, during the forging, theprobability with which the thin-walled portion breaks is increased.Consequently, for maintaining the strength of the thin-walled portion124 a, the widths of the grooves between the protrusions need to belarge to a certain extent, as a result of which limitations are placedon the widths in a peripheral direction of the protrusions of the gearor the vibration member.

The present invention makes it possible to easily mold a plurality ofprotrusions to any width on a metallic processing object, and to reducea load on a mold during the molding of the plurality of protrusions.

According to the present invention, there is provided a method ofproducing a metallic member having a plurality of protrusions. Themethod includes forming a cup-like member by applying a load to ametallic plate member, the load applied to the plate member having acomponent that is perpendicular to a surface of the plate member; andforming the plurality of protrusions at an opening end portion of thecup-like member with a mold by applying a load to the cup-like member,the load applied to the cup-like member having a component that isperpendicular to a surface of a bottom portion of the cup-like member.

According to the present invention, when forming a metallic memberhaving a plurality of protrusions, a cutting operation or a grindingoperation is not required, so that a load on a mold when forming theprotrusions can be reduced. In addition, it is possible form groovesbetween the protrusions of a molded product to any width.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are schematic views showing states in which a cup-likemember is formed according to a first embodiment.

FIGS. 2A to 2D are schematic views showing states in which protrusionsare formed according to the first embodiment.

FIG. 3 is a schematic view of a cup-like member according to a secondembodiment.

FIGS. 4A to 4C are schematic views showing states in which a preliminarymolded product is formed according to the second embodiment.

FIGS. 5A to 5C are schematic views showing states of a final moldingoperation according to the second embodiment.

FIGS. 6A and 6B are schematic views showing a related forging moldingoperation.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will hereunder bedescribed in detail with reference to the drawings. As a metallic memberused in the present invention, a vibration-wave-driving-apparatusvibration member having protrusions for increasing vibrationdisplacement, or a gear having teeth for output transmission is used asan example.

First Embodiment

In a first embodiment, as a metallic member having a plurality ofprotrusions protruding in the same direction, avibration-wave-driving-apparatus vibration member having protrusions forincreasing vibration formed on a surface of the vibration member is usedas an example, to describe a method of producing the vibration member.The vibration wave driving apparatus includes the vibration memberprovided with a piezoelectric element (which is one type ofelectro-mechanical energy conversion element). In the vibration wavedriving apparatus, an alternate signal is supplied to the piezoelectricelement to generate a traveling wave at a surface of the vibrationmember, and the traveling wave is used to drive a moving member thatcontacts the vibration member.

As shown in FIG. 1A, in the embodiment, first, a disc 11-1, formed ofstainless steel (SUS420J2) and being a plate member that has beenpunched out by a pressing operation, is placed at an inside-diameterportion of a positioning plate 26 of a mold for a drawing operation. Inaddition to stainless steel, the metallic member may be formed of, forexample, SPC material, a low alloy steel, a high alloy steel, or anon-ferrous alloy. The drawing mold comprises a punch 22, which is amale mold, and a female mold. The female mold comprises a die 24 havinga recessed portion, a die ring 23 serving as an outer frame and being aholding portion of the die 24, a knockout portion 25 for separating amolded product from the female mold, and a positioning plate 26.

As shown in FIG. 1B, by performing a drawing operation in which thepunch 22 is pushed downward and a load having an out-of-plane component(that is, a component that is perpendicular to a surface of the platemember) is applied, a cup-like member 11-2 is molded as shown in FIG.1C. In the invention, the cup-like member has the form of a containerhaving a bottom portion 52 and a side surface 53 formed along the outerperiphery of the bottom portion 52. A hole or a recess may be formed inthe bottom portion 52. As shown in FIG. 1C, the cup-like member is suchthat the width in a radial direction of an opening end portion 51 issmaller than the width in a radial direction of protrusions (representedby reference numeral 55 in FIG. 2D) of a final molded product, and suchthat the height of the side surface 53 is greater than the height of theprotrusions (that is, the length thereof in a direction perpendicular tothe radial direction) of the final molded product. Though the detailswill be given later, by performing such a molding operation, since thewidth in the radial direction of the opening end portion 51 alsoincreases at the same time that the height of the side surface 53 isbeing reduced, a load that is applied to the molds when forming theprotrusions in a post-processing process is reduced. In addition, thevolume of each protrusion is maintained.

Further, by molding the side surface 53 so that a slope extendingoutward with respect to the bottom portion 52, that is, by forming theopening end portion 51 of the cup-like member so that the outsidediameter of the opening end portion 51 of the cup-like member is largerthan the outside diameter of the bottom portion 52 of the cup-likemember, a molding load is reduced when forming the protrusions in thepost-processing process. Therefore, performing this is desirable. Thisis because, since, as shown in FIG. 2B, the cup-like member is deformedso as to extend outward in the molding process, a load that is appliedto a thin-walled portion 34 a in a height direction is reduced.

Next, for softening the cup-like member 11-2, for example, an annealingheat treatment at a temperature of 750° C. is performed. The heattreatment is performed to reduce molding load during a forging operationperformed for forming the protrusions in the post-processing process, sothat the cup-like member tend to undergo plastic deformation. Dependingupon the extent of drawing, the hardening of the material does notprogress very much and deformation resistance does not increase verymuch. Therefore, the annealing heat treatment may sometimes be omitted.Thereafter, a lubricating treatment may be performed on the surface ofthe cup-like member 11-2. In the lubricating treatment, for example, alubricant whose main component is molybdenum disulfide is applied.

FIG. 2A shows a state in which the cup-like member 11-2 is placed in amold (used for molding the protrusions) and is positioned in the mold.The mold used for molding the protrusions includes a female mold(including a die ring 33, a die 34, and a knockout portion 35) and apunch 32 (serving as a male mold). A groove in which the cup-like memberis inserted is formed along the circumference of the die 34. Thethin-walled portion 34 a, disposed with an equal interval in aperipheral direction, is formed in the groove formed along thecircumference. An inner peripheral wall of the groove has a slope. Thecloser to the bottom portion of the groove, the closer an outerperipheral wall and the inner peripheral wall are to each other, so thatthe width of the groove in the radial direction becomes smaller. Byforming such a groove, as can be seen from FIGS. 2A and 2B, as the punchis moved downward, the opening end portion of the cup-like member tendsto spread outward; and, if the inner peripheral wall has a slope,plastic flow is infrequently hindered. Therefore, this structure isdesirable. When the shape of the mold is one that infrequently hindersplastic flow, the probability with which breakage of the mold and adefect (crack, bending, etc.) in a molded product occur is reduced.

The cup-like member is positioned at an inside-diameter portion of thedie ring 33, and the opening end portion of the cup-like member isdisposed so as to contact the upper end of the thin-walled portion 34 a(a portion of the die 34) for forming grooves between the protrusions.

FIG. 2B shows a state in which, as the punch 32 is moved downward, aload having a component that is perpendicular to the bottom portion ofthe cup-like member is applied, and the cup-like member is beingdeformed. At this stage, a load applied to the punch 32 and thethin-walled portion 34 a is small. However, as the entire form of thecup-like member is deformed and is compressed as indicated by referencenumeral 11-3, protrusions start to form at the opening end portion ofthe cup-like member 11-3. Then, as the punch 32 is moved downward, theload is gradually increased, and the whole molding operation ends at thebottom dead point as shown in FIG. 2C. As a result, a final moldedproduct 11-4 is obtained as shown in FIG. 2D.

By the compression molding performed by this forging operation, theprotrusions 55 are formed at the opening end portion 51 of the cup-likemember, and the width in the radial direction of the protrusions 55becomes greater than the width of the opening end portion of thecup-like member. The thickness of the bottom portion 54 of the finalmolded product is less than the thickness of the bottom portion 52 ofthe cup-like member. Accordingly, in the embodiment, stress applied toeach portion of the molds, in particular, to the thin-walled portion 34a during the molding process is gradually increased, and a force appliedto the thin-walled portion in the peripheral direction is small, so thatthe probability with which the thin-walled portion 34 a is broken isreduced. Since excess metal that is produced as the bottom portion ofthe cup-like member is made thinner is used for forming the protrusionsat the outer peripheral side, the load on the die and the knockoutportion is also reduced, thereby reducing the probability of deformationand breakage thereof. The shape of the side surface of the cup-likemember and the shape of the protrusions are not limited to the shapesdiscussed in the embodiment as long as they can be deformed so that thewidth in the radial direction of the protrusions, that is, the platethickness is increased during the forging operation. For example, theprotrusions may be inclined not only at the inner peripheral side, butalso at the outer peripheral side, or may be formed with the same width.

Further, in the embodiment, as a plate member serving as the processingobject, a plate member having a width that is smaller than the width inthe radial direction of the groove of the die 34 (that is, the width inthe radial direction of the protrusions of the molded product) may beused, thereby reducing costs. The reason will be given below.

In the related method shown in FIG. 6, in order to form a disc(processing object), a round bar is cut in round slices with a hand sawinstead of by a cutting operation. However, in this method, largevariations occur in the thickness of the processing object, and theparallelism of both surfaces is not good. In addition, there are sawmarks on surfaces cut in round slices, so that surface roughness thereofis high. Therefore, variations occur in the thickness of portions of themolded product, in particular, variations in the heights of theindividual protrusions tend to occur. Moreover, the saw marks remain onthe processing object at molded end surfaces, thereby making itnecessary to perform grinding for removing the saw marks. As mentionedabove, in the embodiment, as the processing object, a plate member whosediameter is larger than the diameter of the vibration member (which isthe final molded product) as with the disc 11-1 shown in FIG. 1A andwhich is such that the thickness of the disc 11-1 is less than thethickness of the protrusions of the vibration member may be used.Accordingly, since a rolled plate that is lower in cost than, forexample, a round bar may be used, it is possible to reduce materialroughness and increase the parallelism of both surfaces, and to reducecosts. In addition, since the plate member is thin, little changes occurin the plate thickness when forming the bottom portion to apredetermined thickness (height), so that work hardening does notprogress very much. As a result, the stress that is required forreducing the thickness of the bottom portion is reduced, so thatdeformation and breakage of the die and the knockout portion occur evenless often.

The vibration member formed in accordance with the embodiment makes itpossible for the mass of the protrusions of the vibration member toprovide vibration energy, and to reduce the width of the thin-walledportion in the peripheral direction. Therefore, it is possible to causethe width of the grooves formed between the protrusions that areadjacent to each other to be as small as possible. That is, it ispossible to increase the width in the peripheral direction of theprotrusions, and to increase resistance to wear of the protrusions thatcontact the moving member.

In the vibration wave driving apparatus, if the width in the peripheraldirection of the protrusions formed by the compression molding isincreased, not only is the resistance to wear increased, but alsoundesired vibration is restricted. This is because, since naturalvibration frequency of each protrusion itself is small, undesiredvibration caused by the protrusions themselves infrequently occurs.

In the present invention, the method of molding the cup-like member byapplying a load having a component that is perpendicular to the surfaceof the plate member to the plate member is not limited to drawing. Aslong as it is a method of three-dimensionally deforming the platemember, any other method, such as burring, stretch forming (embossing),or dish extrusion (bowl molding) may also be used.

The method of forming the protrusions by applying a load having acomponent that is perpendicular to the surface of the bottom portion ofthe cup-like member to the cup-like member is not limited to coldforging. The plate member may also be molded by hot forging, warmforging, or cold pressing.

In accordance with the embodiment, a vibration member formed ofstainless steel (SUS420J2), having an outside diameter of 48 mm, whosebottom portion has a thickness of 2.5 mm, whose protrusions have a widthof 5 mm in a radial direction, and whose protrusions have a height of4.5 mm was produced. A mold used for molding the protrusions had aheight of 4.5 mm and a width of 0.6 mm (at a thinnest portion) in aperipheral direction of a thin-walled portion of a die. When an attemptwas made to form such a vibration member by the related method shown inFIGS. 6A and 6B, a load of at least 3 t was required, and a largepressure instantaneously acted upon the thin-walled portion, as a resultof which the probability of breakage of the thin-walled portion washigh. However, when the protrusions were formed using the methodaccording to the embodiment, a load was not instantaneously applied tothe thin-walled portion, or a total load was small, thereby reducing theburden on the mold during the molding.

Second Embodiment

Next, a method of molding protrusions of a vibration member according toa second embodiment will be described. The second embodiment differsfrom the first embodiment in that a hole is formed in the center of abottom portion of a cup-like member and in that a preliminary moldingoperation is performed on the cup-like member between a step of formingthe cup-like member and a step of forming a final molded product.

FIG. 3 is a cup-like member 41-1 after drawing. The cup-like member isopen by press-punching a circular hole 41-1 a in the center of a bottomportion 52. The other features of the cup-like member are the same asthose of the cup-like member according to the first embodiment. Thecircular hole may be formed when a plate member provided prior tomolding the cup-like member is formed, or when the cup-like member ismolded, or after the cup-like member is molded. The circular hole isformed for determining the center position in a next molding step.Therefore, instead of such a through hole, a recess may be formed.

FIG. 4A shows a state in which protrusions are molded by applying a loadhaving a component that is perpendicular to a surface of the bottomportion 52 of the cup-like member to the cup-like member. The circularhole of the cup-like member is fitted to a positioning protrusion 42 a,provided at an end portion of a punch 42, and the center of the cup-likemember 41-1 and the center of a mold coincide with each other. Thisprevents the cup-like member from being decentered when it is beingcompressed. An opening end portion 51 of the cup-like member can berestrained at an inside-diameter portion of a die ring 43, and thebottom portion 52 of the cup-like member, that is, a portion of thecup-like portion that contacts the punch 42 can be secured so as not tobe shifted in a direction parallel to the surface of the bottom portionin FIG. 4A.

The reason that the circular hole is provided to restrain the centerposition in this way is related to the precision of the shape of thecup-like member 41-1 and uniformity in its plastic deformation. Indrawing, considering the plastic deformation of a material itself, theprecision of the shape of a molded product is often influenced by thedegree of its anisotropy. Anisotropy occurs as a result of aggregatestructures differing from each other in connection with, for example,crystal orientation according to material. For example, characteristics,such as stretching, processing hardening coefficient, an elastic limitvalue, and Young's modulus, in a rolling direction differ from those ina direction orthogonal to the rolling direction. As a result,differences also occur in the Lankford value (characteristic valueindicating the anisotropy of a plate material) and a spring-back amount(amount by which the plate material returns to its state prior toprocessing by a slight opposing force after a bending operation). If theplate member having a high anisotropic property is drawn, the openingend portion 51 of the cup-like member may be curled. The opening endportion 51 of such a cup-like member infrequently has a high degree ofcircularity.

To overcome this problem, in the embodiment, measures are taken to allowthe use of a material having a high anisotropic property. That is, inthe embodiment, as mentioned above, for example, a hole that restrainsthe center position is formed in the cup-like member. This causesdeformation in a radial direction to be uniform during the deformationof the cup-like member. As a result, variations in the thickness in aperipheral direction of a molded product that is formed by compressionare reduced.

FIG. 4B shows a state 41-2 in which the cup-like member has beencompressed. The molding step is a preliminary molding step. Here, theshape of a final molded product is not yet formed. Rather, thepreliminary molded product 41-2 having low protrusions, that is, shallowgrooves between the protrusions are formed as shown in FIG. 4C. If sucha preliminary molding is performed, when final protrusions are molded,almost no sideways force is generated at the thin-walled portion,thereby making it possible to reduce the probability of breakage. Thisis like forming a mortar-like recessed portion at a location where thehole is previously formed with a drill to make it possible to fix an endposition of the drill and prevent breakage of the drill when the drillis bent. If shallow grooves are formed at positions where the groovesare previously formed, they function as guides to make it possible toeasily mold final deep grooves, that is, high protrusions.

Prior to molding the final protrusions, it is desirable that thepreliminary molded product be subjected to intermediate heat treatment(annealing). By the heat treatment, the preliminary molded product issoftened, so that deformation resistance is reduced in a final step. Asa result, in addition to reducing the probability of seizure and theburden on the mold used in the final step, the probability of crackingof the molded product itself is reduced. The heat treatment is alsoeffective in reducing negative effects caused by the aforementionedanisotropy as recrystallization occurs.

It is desirable that a lubricating treatment also be performed on thepreliminary molded product 41-2 whose protrusions have small volumes(grooves between the protrusions are shallow). This is because, stresson the molds in the final molding step, in particular, seizure of thethin-walled portion is reduced. In the lubricating treatment, forexample, a lubricant whose main component is molybdenum disulfide isapplied.

FIG. 5A shows a state in which the preliminary molded product is set inthe mold used to mold the shape of the final vibration member. At thistime, it is desirable that the width in the peripheral direction of thegrooves between the protrusions of the preliminary molded product begreater than the width in the peripheral direction of an end portion ofa thin-walled portion 44 a corresponding thereto. By molding such apreliminary molded product, it becomes easier to align in the peripheraldirection the grooves between the protrusions of the preliminary moldedproduct 41-2 and the thin-walled portion 44 a of the die 44. Further, itis possible to increase the thickness of the thin-walled portion of themold used for the preliminary molding, so that breakage occurs lessfrequently.

FIG. 5B shows a state in which the preliminary molded product 41-2 hasbeen pressed until a molded product 41-3 having the final shape isformed. At this time, the circular hole 41-2 a formed in the centralportion of the preliminary molded product becomes a hole 41-3 a of thefinal molded product shown in FIG. 5C. The diameter of the hole 41-3 ais smaller than the diameter of the circular hole 41 -2 a.

As described above, in the embodiment, the circular hole 41-2 a isformed in the center of the bottom portion of the cup-like member, andthe preliminary molding step is provided prior to the step of formingthe final protrusions. Forming the circular hole makes it possible torestrain the center position and to reduce variations in the width ofthe molded product in the peripheral direction. In addition, even in thefinal molding step, when a load having an out-of-plane component isapplied, the circular hole makes it possible for excess metal to be usedfor the circular hole and to prevent excessive stress from being appliedto the molds. In addition, by providing the preliminary molding step,when the final protrusions are being molded, almost no sideways force isgenerated at the thin-walled portion, thereby making it possible tofurther reduce the probability of breakage.

Although each of the embodiments is described taking as an example thecase in which protrusions for increasing vibration in the vibrationmember are formed, the present invention is not limited thereto. Thatis, as long as a metallic processing object having a plurality ofprotrusions protruding in one direction is provided, the above-describedmolding method is applicable to parts having shapes similar to those of,for example, a bevel gear and a hypoid gear.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2009-172920 filed Jul. 24, 2009, which is hereby incorporated byreference herein in its entirety.

1. A method of producing a metallic member having a plurality ofprotrusions, the method comprising: forming a cup-like member byapplying a load to a metallic plate member, the load applied to theplate member having a component that is perpendicular to a surface ofthe plate member; and forming the plurality of protrusions at an openingend portion of the cup-like member with a mold by applying a load to thecup-like member, the load applied to the cup-like member having acomponent that is perpendicular to a surface of a bottom portion of thecup-like member.
 2. The method of producing the metallic memberaccording to claim 1, wherein the cup-like member is formed so that anoutside diameter of the opening end portion of the cup-like member islarger than an outside diameter of the bottom portion of the cup-likemember.
 3. The method of producing the metallic member according toclaim 1, further comprising preliminarily molding a groove that isshallower than a groove that is formed between the plurality ofprotrusions, the step of preliminarily molding the shallower groovebeing performed between the step of forming the cup-like member and thestep of forming the plurality of protrusions.
 4. The method of producingthe metallic member according to claim 3, further comprising performingheat treatment between the step of preliminarily molding the shallowergroove and the step of forming the plurality of protrusions.
 5. Themethod of producing the metallic member according to claim 1, whereinthe cup-like member has a hole or a recess at the center of the bottomportion thereof.
 6. The method of producing the metallic memberaccording to claim 1, wherein the plate member has a thickness that isless than a width in a radial direction of the protrusions.
 7. Themethod of producing the metallic member according to claim 1, whereinthe cup-like member is molded so that a width in a radial direction ofthe opening end portion of the cup-like member is less than a width in aradial direction of the protrusions.
 8. The method of producing themetallic member according to claim 1, wherein the step of forming thecup-like member is performed by any one of drawing, burring, stretchforming, and dishing.
 9. The method of producing the metallic memberaccording to claim 1, wherein the step of forming the plurality ofprotrusions is performed by either forging or cold pressing.
 10. Amethod of producing a metallic member comprising: forming a cup-likemember by applying a load to a metallic plate member; and forming aplurality of protrusions at an opening end portion of the cup-likemember by placing the cup-like member into a mold.
 11. The method ofproducing the metallic member according to claim 10, wherein thecup-like member is formed so that an outside diameter of the opening endportion of the cup-like member is larger than an outside diameter of abottom portion of the cup-like member.
 12. The method of producing themetallic member according to claim 10, further comprising preliminarilymolding a groove that is shallower than a groove that is formed betweenthe plurality of protrusions, the step of preliminarily molding theshallower groove being performed between the step of forming thecup-like member and the step of forming the plurality of protrusions.13. The method of producing the metallic member according to claim 12,further comprising performing heat treatment between the step ofpreliminarily molding the shallower groove and the step of forming theplurality of protrusions.
 14. The method of producing the metallicmember according to claim 10, wherein the cup-like member has a hole ora recess at the center of a bottom portion thereof.
 15. The method ofproducing the metallic member according to claim 10, wherein the platemember has a thickness that is less than a width in a radial directionof the protrusions.
 16. The method of producing the metallic memberaccording to claim 10, wherein the cup-like member is molded so that awidth in a radial direction of the opening end portion of the cup-likemember is less than a width in a radial direction of the protrusions.